The present invention relates to a process for the manufacture of shaped articles, of any desired shape, from polyolefine compositions comprising polyolefines modified by means of polar monomers, and high contents of cellulosic fibres.
Belgian Pat. No. 860,469 filed on Nov. 4, 1977 in the name of the Solvay & Cie. has already disclosed a process for the manufacture, from the above-mentioned polyolefine compositions, of particular shaped articles, namely composite panels comprising metal foils which are combined by hot-pressing with polyolefine sheets consisting of the above-mentioned polyolefine compositions.
According to this known process, the polyolefine compositions can be prepared and converted to sheets when they are at temperatures just above the melting points of the polyolefines employed. Thereafter, the polyolefine sheets are brought into contact with the metal foils and subjected to a pressing operation which is carried out at temperatures markedly higher than the melting points of the polyolefines employed. It is during this pressing operation that the extremely high adhesion between the polyolefine sheets and the metal foils, which characterises the panels in question, develops. This very high adhesion results from the conjoint use of polyolefines modified with polar monomers, and of cellulosic fibres. It goes without saying that this known process is limited in its applications to the manufacture of articles having certain particular shapes and having a particular constitution.
It is furthermore known, from British Pat. No. 1,479,335 filed on Nov. 20, 1974 in the name of MITSUBISHI PETROCHEMICAL Co LIMITED, to shape polyolefine compositions comprising polyolefines modified by means of polar monomers and low contents of cellulosic fibres by malaxating at temperatures markedly greater than the melting points of the polyolefines employed. The shaped articles obtained from such polyolefine compositions have inadequate mechanical properties for numerous applications.
Finally, the shaped articles obtained from polyolefine compositions comprising high contents of polyolefines modified with polar monomers and of cellulosic fibres, shaped by malaxating at temperatures just above the melting points of the polyolefines employed, also exhibit inadequate properties for numerous applications.